The present invention relates to aircraft takeoff and landing arrangements, more particularly to ground-effect landing gears. It can be used with particular advantage on aircraft intended for performing takeoff and landing on unprepared soft ground.
It is known that first in the world practice an attempt to use a ground-effect arrangement instead of a conventional wheeled undercarriage was made in the U.S.S.R. in the 1930s on an UT-2 (YT-2) airplane intended for performing takeoff and landing on unprepared soft ground.
In the U.S.A. a ground-effect landing gear was first produced by the Bell firm and mounted on a small LA-4 amphibian plane whose first flight was made in August 1967. However, this landing gear can be used only on paved surfaces or on water because the gas pressure of the air cushion involved exceeds the critical point as regards ground destruction.
In the present time research is carried out with the view of improving ground-effect landing gears so as to make them suitable for use on modern high-speed and high power/weight ratio aircraft.
Known in the prior art are ground-effect landing gears (see, for example, U.S. Pat. No. 3275270, class 244-110, the year 1966) comprising a platform mounting a flexible enclosure constructed in the form of a sytem of inflatable envelopes bounding an overpressure space near the ground surface. During transition to hovering and during movement of the aircraft said overpressure space is kept in communication with a source of compressed air.
In such ground-effect landing gears the flexible enclosure is constructed as an inflatable tube having a continuous toroidal form, as seen in plan, and attached to the lower surface of the aircraft fuselage.
During transition to hovering and during movement compressed air is supplied from the aircraft source first into the flexible enclosure for inflating same and then, after building up pressure above atmospheric, is discharged through a multiplicity of holes provided in the bottom portion of the enclosure around the perimeter thereof, whereby a circular air curtain is created which, in conjunction with the flexible enclosure, forms an air cushion space under the aircraft fuselage.
By virtue of said air curtain, when the ground surface is in sufficient proximity, the compressed air supplied into the air cushion space creates overpressure supporting the craft in the air.
In cruise the supply of compressed air into the flexible enclosure and air cushion space is discontinued and the enclosure is retracted into a hatch provided in the aircraft fuselage.
One of the main disadvantages of such ground-effect landing gears is that their use on medium and, particularly, heavy airplanes performing takeoff and landing on unpaved soft ground causes ground destruction and, consequently, substantial dust formation due to high-velocity air discharge from inside the inflatable enclosure and the air cushion space.
The landing gears under consideration also suffer from the disadvantage that the mean static pressure of compressed air inside the flexible enclosure has to be maintained much higher than that in the air cushion space, owing to which the deflection of the rear portion of the flexible enclosure caused by increase in the aircraft angle of attack at the end of the takeoff run gives rise to an enclosure righting moment which interferes with the increase in the angle of attack.
This condition makes it difficult to obtain optimum angles of attack during the takeoff run of the aircraft and thereby makes for increasing the takeoff run and the required length of the runway.
It is an object of the present invention to provide an aircraft ground-effect landing gear which will enable an aircraft of any weight category to take off and land without destroying the ground surface involved and, consequently, without considerable dust formation.
It is a further object of the present invention to provide an aircraft ground-effect landing gear which will enable the aircraft angle of attack to be varied during the takeoff run and thereby permit of decreasing the takeoff run and the required runway length.
It is a still further object of the present invention to provide a more compact ground-effect landing gear.
It is a still further object of the present invention to provide a ground-effect landing gear which will ensure directional stability of the aircraft throughout the takeoff and landing runs and at the same time will reduce dynamic loads on the taxi-ing wheels.